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| Author |
Message |
    
Roger
| | Posted on Tuesday, February 05, 2002 - 12:49 pm: | 
|
Looking for a chart or guideline to correctly size the prop on my 1975 Johnson 115HP.
Looking to cruise the bay & rivers fishing (speed)
and also to ski (power).
Can anyone help with a recommendation? |
Jon
| | Posted on Friday, February 08, 2002 - 11:52 am: |
|
Roger,
I don't have a guideline, but if you post up the length, weight, and type of boat I could give you a ballpark, or someone else may know for sure what you need. One thing to keep in mind is it's more or less a trade off between power in speed; they do make props that work better for different purposes, but I think the most important thing to consider is how you are gearing the engine.
Gear it down (lower pitched prop) and you get more "out of the hole" power, higher RPM's at wide open throttle, and possibly some loss in speed. Gear it up (higher pitched prop) you'll get a slower "out of the hole" start, lower RPM's at top speed and possibly a little more on the top end. Your engine has an operating RPM range, most of the time you shoot for the prop that'll give you something close to the top of that with a light load; with a heavier load you can still maintain acceleration that way.
Jon |
Roger
| | Posted on Sunday, February 10, 2002 - 05:59 pm: |
|
i'm running an 18ft V-hull - closed bow w/115 HP Johnson |
Jon
| | Posted on Monday, February 18, 2002 - 11:46 am: |
|
Roger,
Sorry it took me a few to get back to you; Here's the results I found from www.miwheel.com, the Michigan Wheel website. You should check this site out for yourself, but I'd say a 3 X 13 X 19 or 3 X 14 X 19 would be about right.
A couple things thing you should take into consideration are that these results are for any 1973-1995 115; they have a "pleasure model" listed that uses a v6 gearcase and was built after 1994. If you have something 1995 or newer, and it is this "pleasure model", it would make a difference. Secondly, there is also a 21 pitch prop listed for 15-18ft boats, I think it would be a little too high if what you are powering is a fiberglass hull, but if it's an aluminum hull (lighter), you may be able to get away with a 21 pitch. Lastly, these are the specs for an aluminum prop, it may make a difference with stainless props (less flex, more weight).
Propeller Type: Outboard
Manufacturer : EVINRUDE, JOHNSON
HP / Model : 115 HP
Year : 1973-PRESENT
Boat Size : 17'-19' BOATS - ALL LOADS, SKIBOATS
Material : ALUMINUM
Blades Diameter & Pitch Rotation Part number Style Comments
3 13 X 19 RH 011004 MICHIGAN MATCH V-4 GEARCASE PROPELLERS ONLY-THRU HUB EXHAUST
3 14 X 19 RH 011025 MICHIGAN MATCH V-4 GEARCASE PROPELLERS ONLY-THRU HUB EXHAUST |
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